"We expect the summit will confirm the denuclearisation will [of North Korea], and hope to have a comprehensive agreement with the North on the matter". If they don't the summit with the North Korean leader might not happen, he added.
According to CNBC, North and South Korean authorities are in talks to end hostilities ahead of next week's historic meeting between communist dictator Kim Jong Un and South Korean President Moon Jae-in.
Trump said he will meet with Kim in "early June or before that assuming things go well".
It's unclear at this time when they will hold their first conversation, but Moon's chief of staff Im Jong-seok says it's possible they may speak together on the phone this Friday, according to Bloomberg. When the two leaders meet on April 27, they would theoretically have to hash out several issues, from the submarines on the peninsula's coasts to the USA military presence.
The U.S., Japan and South Korea have forged an alliance to get Kim to abandon his nuclear weapons program. It conducted its most powerful nuclear test past year and has sought to develop a missile capable of hitting the US mainland.
Trump also suggested he was responsible not only for the negotiations on a formal peace treaty ending the war but also the success of this year's winter Olympics in South Korea.
International Monetary Fund says global economy will slow after 2019 on escalating trade tensions
The global smartphone boom that's helped propel Asia's economic growth and reshape trade channels in recent years may have peaked. According to the IMF's World Economic Outlook (WEO) report, the country's economic growth is expected to be 7.8 per cent in 2019.
Delegations from the North and the South have been holding meetings prior to the high-level talks to discuss a joint statement.
Moon has been reviewing a framework of the statement which could be called the April 27 declaration or the Panmunjom declaration, he said. Two previous meetings in 2000 and 2007 focused on political and economic issues.
"Without U.S. support and agreement, it will be hard to follow through on inter-Korean agreements".
A successful summit between the Koreas later this month could help pave the way for a meeting between Kim and President Donald Trump.
The war began in 1950. The United States stations 28,500 troops in South Korea as a legacy of the conflict.